Function
Heparan sulfate proteoglycans (HSPGs) are widely expressed throughout most tissues of nearly all multicellular species. The function of HSPGs extends beyond providing an extracellular matrix (ECM) structure and scaffold for cells. They are integral regulators of essential cell signaling pathways affecting cell growth, proliferation, differentiation, and migration. Although the core protein is important, the large heparan sulfate (HS) chains extending from the core are responsible for most receptor signaling. HS chains are heterogeneous structures that differ in specific and conditional cell contexts. Of particular importance is the HS sulfation pattern, which was once thought to be static after HS biosynthesis in the Golgi. However, this paradigm changed after the discovery of two extracellular 6-O-S glucosamine arylsulfatases, Sulf1 and Sulf2. These two enzymes allow rapid extracellular modification of sulfate content in HSPGs, impacting signaling involving Shh, Wnt, BMP, FGF, VEGF, HB-EGF, GDNF, and HGF. In addition, Sulfs may exercise another level of regulation over HS composition by down or upregulating HS biosynthetic enzymes present in the Golgi through the very same signaling pathways they modify.
Read more about this topic: SULF1
Famous quotes containing the word function:
“We are thus able to distinguish thinking as the function which is to a large extent linguistic.”
—Benjamin Lee Whorf (1897–1934)
“The mother’s and father’s attitudes toward the child correspond to the child’s own needs.... Mother has the function of making him secure in life, father has the function of teaching him, guiding him to cope with those problems with which the particular society the child has been born into confronts him.”
—Erich Fromm (1900–1980)
“The information links are like nerves that pervade and help to animate the human organism. The sensors and monitors are analogous to the human senses that put us in touch with the world. Data bases correspond to memory; the information processors perform the function of human reasoning and comprehension. Once the postmodern infrastructure is reasonably integrated, it will greatly exceed human intelligence in reach, acuity, capacity, and precision.”
—Albert Borgman, U.S. educator, author. Crossing the Postmodern Divide, ch. 4, University of Chicago Press (1992)